1. Field of the Invention
The present invention relates to a solid-state laser device, and in particular, to a solid-state laser device having a laser chamber storing a laser rod and an excitation lamp.
The present invention also relates to a photoacoustic measurement device including the solid-state laser device.
2. Description of the Related Art
Hitherto, as one kind of image inspection method which can noninvasively inspect a state inside a living body, an ultrasonography method has been known. In ultrasonography, an ultrasound probe which can transmit and receive an ultrasonic wave is used. If an ultrasonic wave is transmitted from the ultrasound probe to a subject (living body), the ultrasonic wave advances through the inside of the living body, and is reflected from a tissue interface. The reflected ultrasonic wave is received by the ultrasound probe, and a distance is calculated based on the time until the reflected ultrasonic wave returns to the ultrasound probe, whereby it is possible to image the status of the inside.
Furthermore, photoacoustic imaging which images the inside of a living body using a photoacoustic effect is known. In general, in photoacoustic imaging, the inside of the living body is irradiated with pulse laser light. Inside the living body, a living body tissue absorbs energy of pulse laser light, and an ultrasonic wave (photoacoustic wave) is generated due to adiabatic expansion caused by energy. The photoacoustic wave is detected by an ultrasound probe or the like, and a photoacoustic image is constituted based on a detection signal, whereby it is possible to visualize the inside of the living body based on the photoacoustic wave.
In a measurement of a photoacoustic wave, in many cases, it is necessary to emit pulse laser light with high intensity, and a flash lamp excited solid-state laser device is widely used for a light source. The solid-state laser device has a laser rod (laser medium), and a flash lamp (excitation lamp) which excites the laser rod. The laser rod and the excitation lamp are stored inside a laser chamber. The inside of the laser chamber is provided with a reflection surface which allows efficient irradiation of the laser rod with light emitted from the flash lamp or a diffuser which diffuses light and uniformly transmits light to the laser rod.
In the solid-state laser device, if dust or dirt sticks to an end surface of the laser rod or a reflection surface of a resonator mirror, the energy of laser light is concentrated on this portion, the rod end surface or the mirror reflection surface may be damaged. In order to protect the laser rod or the resonator mirror from dust or dirt, a structure in which a laser rod or a resonator mirror is stored in a boxlike base and the top of the base is covered with a lid to seal the inside of the base airtight is considered (for example, see JP1994-260701A (JP-H06-260701A)).